An engine may misfire from time t0 time due to various operating conditions. For example, an engine may misfire in response to a lean engine air-fuel ratio. Further, the engine may misfire in response to improperly timed ignition spark. One way to determine whether or not the engine may have misfired may be by monitoring engine acceleration during an engine cycle. If engine acceleration during an engine cycle is less than a threshold, it may be judged that the engine has misfired. However, there may be some engine operating conditions where it may be difficult to assess whether or not an engine has misfired because the engine may exhibit torsional vibrations of the engine's crankshaft. If engine misfire is not determined during these engine operating conditions, engine torque output may decline and undesirable engine emissions may increase. Therefore, it would be desirable to provide a way of diagnosing the presence or absence of engine misfire over a wider range of engine operating conditions.
The inventors herein have recognized the above-mentioned issues and have developed an engine operating method, comprising: adjusting an engine actuator via a controller in response to engine misfire indicated from engine crankshaft position while operating an engine in a first operating region; and adjusting the engine actuator via the controller in response to engine misfire indicated from output of a sensor coupled to an engine compression ratio adjusting linkage while operating the engine in a second operating region.
By adjusting an engine actuator responsive to engine misfire indicated by engine crankshaft position and output of a sensor coupled to an engine compression ratio adjusting linkage, it may be possible to determine the presence and absence of engine misfire over a larger engine operating range (e.g., an engine speed and load range). For example, engine misfire may be determined from converting engine position into engine speed and differentiating engine speed to determine engine acceleration during engine operating conditions when engine crankshaft torsional vibrations are low. Further, engine misfire may be determined from output of a sensor coupled to an engine compression ratio changing linkage during engine operating conditions when crankshaft torsional vibrations are high. The engine compression ratio changing linkage sensor output may provide a better signal to noise ratio than an engine crankshaft position sensor during some engine operating conditions, and the engine crankshaft position sensor may provide a better signal to noise ratio than the engine compression ratio changing linkage sensor output during other engine operating conditions.
The present description may provide several advantages. Specifically, the approach may provide improved engine misfire detection and mitigation. In addition, the approach may suspend or change methods for determining engine misfire during conditions where one engine misfire detection method may be less reliable. Further, the approach may improve engine emissions and torque production if an engine misfire occurs.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.